The possible alteration of active Ca ions transport mechanism of membrane in sickle red blood cell will be investigated. It was found that the active extrusion of Ca ions from the resealed red cell in the presence of ATP was depressed in sickle cells. Various experimental conditions such as different concentrations of Ca ions and other ions in the incubation medium will be studied with regard to their influence on the Ca ions extrusion mechanism of sickle cell. Detailed mechanisms such as Ca ions binding to the transport enzyme and the level of phosphorylated intermediaries during the active transport will be investigated with sickle cell membrane and results will be compared to those obtained with normal red blood cell membrane. The alteration of Ca ions contents of cell and membrane during sickling processes of sickle cell will be measured to ascertain the role of Ca ions in the induction of irreversibly sickled state. The hypothesis that an increase in Ca ions content of cell membrane may induce irreversible contractile processes of the "contractile proteins" of erythrocyte membrane in the presence of deoxy-HbS will be examined through the analysis of Ca ions data obtained with membrane and "contractile proteins" during the induction of irreversibly sickled state.